In the process of rotary drilling of wells, a variety of abnormal forces can cause stress on the drill string members which comprise the drill string assembly. If these abnormal forces or loads occur repetitively, they can cause failure of the drill string assembly. Down hole vibration and torque have long been associated with bit-failure and drill string failure. These various events are described as stick/slip, bit whirl, bit bounce, and bottom-hole-assembly (BHA) whirl and resonance. Although highly cost-effective, the development and deployment of new slimhole drilling techniques has been hampered by mechanical problems resulting from bit whirl and stick-slip problems.
Directional drilling programs have introduced other problems associated with various shock fatigue factors. The use of downhole motors for driving the drill bit has also been delayed because of vibrational problems associated with the forces described herein.
Although these events have long been recognized as a cause of drill string failures and a variety of tools have been developed to limit or eliminate these shocks, no generally acceptable device has been developed which is capable of absorbing the damaging overload stresses from repetitive longitudinal and rotary shocks.
A number of prior art devices have been proposed to absorb shocks in a drill or pipe string. For example, U.S. Pat. Nos. U.S. Pat. No. 2,212,153 to Eaton (1940) (relating to sucker rod vibrations only), U.S. Pat. No. 2,756,022 to Sturgeon (1956), 3,871,193 to Young (1975), U.S. Pat. No. 3,998,443 to Webb (1976), 4,600,062 to Teng (1986) and U.S. Pat. No. 4,844,181 to Bassinger (1989), each describe devices or combinations of devices to absorb axial or longitudinal shock, yet allow torque transmission to the drill string. U.S. Pat. No. 3,998,443 to Webb (1976) discloses an arrangement to absorb both longitudinal and torque shock, but limited excessive torque by translation of the torque into longitudinal movement. Thus, this patent did not independently absorb both torque and longitudinal shock in the drill string.